Intact and/or freeze-thawed microalgal biomass of Chlamydomonas reinhardtii, Chlorella pyrenoidosa, and Dunaliella tertiolecta were liquefied using a starch-hydrolyzing lactic acid bacterium, Lactobacillus amylovorus, in order to obtain an ideal substrate for H-2 production by the photosynthetic bacterium Rhodobacter sphaeroides RV. Starch accumulated in the algal biomass was converted to H-2 with a high, conversion yield of 5 mol H-2/mol of starch glucose. In this system, the rigid algal cell wall structure could be degraded without the need for any physicochemical or enzymic pretreatment; L. amylovorus appeared to play a role in this degradation.